From Philips computer monitors in the market the feature lightframe™ is known. This feature enables the user to select an area on the screen of a display device in which the brightness should be increased. This is especially advantageous if natural information is displayed in the area. Natural information comprises photos and films which typically have a lower resolution than synthetic information such as text. The perceptual quality of this low resolution information improves considerably by increasing the brightness. On the other hand, the brightness of the high resolution synthetic information should not be increased to avoid blurring.
Usually, the area is a window or a part of a window created by the operating system Microsoft Windows or by an application running on the operating system. The area to be enhanced is further referred to as enhancement area.
In cathode ray tubes, the increased brightness is created by increasing the beam current in the cathode ray tube locally in the high brightness area.
In liquid crystal displays, the maximum brightness is determined by the light output of the backlighting. If the light output of the enhancement area has to be increased, the light output of the backlighting has to be increased, and the data outside the enhancement area has to be adapted (dimmed) to keep the brightness substantially constant outside the enhancement area.